1. Field of the Invention
The present invention relates to an earth globe.
2. Description of the Prior Art
A conventional earth globe includes a spherical globe body on which a map is drawn. The globe body is rotatably supported by a base around an axis which is inclined relative to a vertical axis and which corresponds to the earth axis. A user can therefore refer to a particular part of the map by rotating the globe body, and such rotation may represent the rotation of earth.
In some designs, the earth globe is so constructed as to show a day region and a night region on the earth. Such an earth globe includes a hollow spherical globe body made of translucent material. The spherical globe body includes a lamp and a shading plate therein. The shading plate serves to prevent a predetermined half area of the spherical globe body from being irradiated by light of the lamp. With this construction, when the lamp is lit, the predetermined half area shaded by the shading plate is dark as viewed from the outside, while the remaining half is bright due to the irradiation of light. Therefore, the user can distinguish the day and night areas from each other based on the state that the light is irradiated thereto or not.
Meanwhile, the earth revolves around the sun or performs an orbital movement while rotating around its own axis or the earth axis. Since the earth axis is inclined relative to the axis perpendicular to the orbital plane of the earth, the light from the sun is irradiated to the earth in different ways in response to changes of position of the earth along the revolution orbit (changes of the season). Therefore, in order to show the change of night and day (change in the direction of sunlight) in response to changes of the season, the user requires to change the position of the lamp as well as the position of the shading plate within the spherical globe body.
Earth globes shown in FIGS. 5 and 6 have been proposed to permit such changes of positions of the lamp and the shading plate. The earth globe shown in FIG. 5 includes a spherical globe body E rotatable around an axis corresponding to the earth axis. A vertical shaft J is disposed within the spherical globe body E and extends through the center of the spherical globe body E. A lamp L and a shading plate P are mounted on the vertical shaft J. A knob T manually operable by the user is disposed outside of the spherical globe body E. A gear mechanism H is disposed within the spherical globe body E for transmitting rotation of the knob T to the vertical shaft J. Thus, when the user turns the knob T, the lamp L as well as the shading plate P is rotated together with the vertical shaft J, so that the area to be irradiated can be changed.
The construction of the earth globe shown in FIG. 6 is the substantially same as the earth globe shown in FIG. 5 except the arrangement of the gear mechanism H and the knob T.
With the above conventional earth globes shown in FIGS. 5 and 6, the lamp L and the shading plate P are rotated manually and independently of the rotation of the spherical globe body E, and therefore, it is difficult for the user to understand the correlation between the rotation and the revolution of the earth. Further, since the operation for rotating the spherical globe body E and that for rotating the knob T must be performed separately from each other, such operations are very troublesome. Additionally, for this reason, the user cannot observe the continuous change of day and night in the earth over a long period of time such as one year.
Therefore, these conventional earth globes will not provide a sufficient study aid. Further, they are not amusing since they do not change their appearances unless they are manually operated by the user. For the same reason, they are not suitable for use as interior ornamental articles.